/*
 * dlep.c
 *
 * Dynamic Link Exchange Protocol
 * 
 * Copyright (C) 2024 - ntop.org
 * Copyright (C) 2024 - V.G <v.gavrilov@securitycode.ru>
 *
 * This file is part of nDPI, an open source deep packet inspection
 * library based on the OpenDPI and PACE technology by ipoque GmbH
 *
 * nDPI is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * nDPI is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with nDPI.  If not, see <http://www.gnu.org/licenses/>.
 * 
 */

#include "ndpi_protocol_ids.h"

#define NDPI_CURRENT_PROTO NDPI_PROTOCOL_DLEP

#include "ndpi_api.h"
#include "ndpi_private.h"

static void ndpi_int_dlep_add_connection(struct ndpi_detection_module_struct *ndpi_struct,
                                         struct ndpi_flow_struct *flow)
{
  NDPI_LOG_INFO(ndpi_struct, "found DLEP\n");
  ndpi_set_detected_protocol(ndpi_struct, flow,
                             NDPI_PROTOCOL_DLEP, NDPI_PROTOCOL_UNKNOWN,
                             NDPI_CONFIDENCE_DPI);
}

static void ndpi_search_dlep(struct ndpi_detection_module_struct *ndpi_struct,
                             struct ndpi_flow_struct *flow)
{
  struct ndpi_packet_struct const * const packet = &ndpi_struct->packet;

  NDPI_LOG_DBG(ndpi_struct, "search DLEP\n");

  if (packet->udp != NULL && packet->payload_packet_len > 27) {
    if ((memcmp(packet->payload, "DLEP", 4) == 0)) {
      ndpi_int_dlep_add_connection(ndpi_struct, flow);
      return;
    }
  } else if (packet->tcp != NULL) {
    /* Maybe it's unnecessary, but it'll definitely eliminate any false positives. 
     * 854 port is IANA registered for DLEP. */
    if (packet->payload_packet_len > 8 &&
        (ntohs(packet->tcp->dest) == 854 || ntohs(packet->tcp->source) == 854))
    {
      if (ntohs(get_u_int16_t(packet->payload, 0)) < 0x11 &&
          ntohs(get_u_int16_t(packet->payload, 2)) == (u_int16_t)(packet->payload_packet_len-4))
      {
        ndpi_int_dlep_add_connection(ndpi_struct, flow);
        return;
      }
    }
  }

  NDPI_EXCLUDE_DISSECTOR(ndpi_struct, flow);
}

void init_dlep_dissector(struct ndpi_detection_module_struct *ndpi_struct)
{
  register_dissector("DLEP", ndpi_struct,
                     ndpi_search_dlep,
                     NDPI_SELECTION_BITMASK_PROTOCOL_V4_V6_TCP_OR_UDP_WITH_PAYLOAD_WITHOUT_RETRANSMISSION,
                     1, NDPI_PROTOCOL_DLEP);
}
